Brother, you are asking excellent questions about the message, which Hebrews 3 and 4 answers! The opponents are well defined in the message of Hebrews 3 and 4:
- Those whose corpses lay in the wilderness who were unable to enter God's rest for 40 years.
- Us in the new covenant with Jesus as our High Priest who can enter God's rest if we benefit from God not allowing them to enter the Sabbath during those 40 years with Manna that did Joshua no good.
The "good news" that both opponents have is not the Gospel of Jesus, but how God did not allow them to enter the Sabbath during those 40 years with Manna that did Joshua no good. The news of how God did not allow those whose corpses lay in the wilderness to enter the Sabbath during those 40 years near the Promised Land, can help us to enter the Sabbath under the new covenant when Jesus finally rescues His Sabbath from the human tradition of Judaism about the Sabbath since Joshua.
We under the new covenant can listen to the instructions that did Joshua no good. We can listen to the instructions God gave both opponents during the 40 years with Manna about how God did not allowed those whose corpses lay in the wilderness to enter His Sabbath. What was available to both is not the new covenant but the instructions during the Manna, which did Joshua no good but can do us good under the new covenant, with Jesus correcting the human tradition of Judaism since Joshua.
The Sabbath was not entered during those 40 years with Manna by those whose corpses lay in the wilderness, even though they kept the seventh day of the week, because they were keeping the wrong Sabbath near the Promised Land as punishment during those 40 years by "oath" that they later entered with Joshua in the Promised Land at a different time, though under Joshua they wrongly assumed that this other time was the seventh day of the week. They entered but did not have God's rest because of their wrong assumption about the Sabbath in the Promised Land being the seventh day of the week since Joshua.
Joshua was the leader that replaced Moses and led them to the Promised Land when they entered God's Sabbath at a different time than with Manna, but wrongly assumed that it was the seventh day of the week in the Promised Land, so that they did not have God's rest to keep the Sabbath outside of the time zone of the Promised Land.
Joshua failed by wrongly assuming that the Sabbath in the Promised Land was the seventh day of the week when God instructed, during the 40 years with Manna, that keeping the Seventh day near the Promised Land did not enter the Sabbath, that they later enter at a different time in the Promised Land that was not the seventh day of the week as they wrongly assumed.
God spoke of another day through David but it was not understood until He explained it in Hebrews 3 and 4 under the new covenant to finally rescue His Sabbath from the human tradition of Judaism since Joshua. Why did God wait until the new covenant to correct this human tradition? The correction was not necessary while the faithful were in the Promised Land, but under the new covenant, when we are outside the Promised Land, it becomes important to correct the Sabbath for us to enter the Sabbath outside the time zone of the Promised Land. The following is further confirmation that the Sabbath in the Promised Land is not a weekday but falls earlier between two weekdays.
long after the Sabbath (evening), as it dawns beyond Saturday (morning), came Mary Magdalene and the other Mary, to see the tomb. (Mathew 28:1, my own translation)
United in our hope for the soon return of Jesus, Jorge